xref: /freebsd/usr.bin/netstat/if.c (revision b17b639832e707aab0e9514cf94727498e2d67bd)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 2013 Gleb Smirnoff <glebius@FreeBSD.org>
5  * Copyright (c) 1983, 1988, 1993
6  *	The Regents of the University of California.  All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. Neither the name of the University nor the names of its contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  */
32 
33 #if 0
34 #ifndef lint
35 static char sccsid[] = "@(#)if.c	8.3 (Berkeley) 4/28/95";
36 #endif /* not lint */
37 #endif
38 
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
41 
42 #include <sys/param.h>
43 #include <sys/protosw.h>
44 #include <sys/socket.h>
45 #include <sys/socketvar.h>
46 #include <sys/time.h>
47 
48 #include <net/if.h>
49 #include <net/if_dl.h>
50 #include <net/if_types.h>
51 #include <net/ethernet.h>
52 #include <netinet/in.h>
53 #include <netinet/in_var.h>
54 #include <arpa/inet.h>
55 #ifdef PF
56 #include <net/pfvar.h>
57 #include <net/if_pfsync.h>
58 #endif
59 
60 #include <err.h>
61 #include <errno.h>
62 #include <ifaddrs.h>
63 #include <libutil.h>
64 #ifdef INET6
65 #include <netdb.h>
66 #endif
67 #include <signal.h>
68 #include <stdbool.h>
69 #include <stdint.h>
70 #include <stdio.h>
71 #include <stdlib.h>
72 #include <string.h>
73 #include <sysexits.h>
74 #include <unistd.h>
75 #include <libxo/xo.h>
76 
77 #include "netstat.h"
78 
79 static void sidewaysintpr(void);
80 
81 #ifdef PF
82 static const char* pfsyncacts[] = {
83 	/* PFSYNC_ACT_CLR */		"clear all request",
84 	/* PFSYNC_ACT_INS_1301 */	"13.1 state insert",
85 	/* PFSYNC_ACT_INS_ACK */	"state inserted ack",
86 	/* PFSYNC_ACT_UPD_1301 */	"13.1 state update",
87 	/* PFSYNC_ACT_UPD_C */		"compressed state update",
88 	/* PFSYNC_ACT_UPD_REQ */	"uncompressed state request",
89 	/* PFSYNC_ACT_DEL */		"state delete",
90 	/* PFSYNC_ACT_DEL_C */		"compressed state delete",
91 	/* PFSYNC_ACT_INS_F */		"fragment insert",
92 	/* PFSYNC_ACT_DEL_F */		"fragment delete",
93 	/* PFSYNC_ACT_BUS */		"bulk update mark",
94 	/* PFSYNC_ACT_TDB */		"TDB replay counter update",
95 	/* PFSYNC_ACT_EOF */		"end of frame mark",
96 	/* PFSYNC_ACT_INS_1400 */	"state insert",
97 	/* PFSYNC_ACT_UPD_1400 */	"state update",
98 };
99 
100 static const char* pfsyncacts_name[] = {
101 	/* PFSYNC_ACT_CLR */		"clear-all-request",
102 	/* PFSYNC_ACT_INS_1301 */	"state-insert-1301",
103 	/* PFSYNC_ACT_INS_ACK */	"state-inserted-ack",
104 	/* PFSYNC_ACT_UPD_1301 */	"state-update-1301",
105 	/* PFSYNC_ACT_UPD_C */		"compressed-state-update",
106 	/* PFSYNC_ACT_UPD_REQ */	"uncompressed-state-request",
107 	/* PFSYNC_ACT_DEL */		"state-delete",
108 	/* PFSYNC_ACT_DEL_C */		"compressed-state-delete",
109 	/* PFSYNC_ACT_INS_F */		"fragment-insert",
110 	/* PFSYNC_ACT_DEL_F */		"fragment-delete",
111 	/* PFSYNC_ACT_BUS */		"bulk-update-mark",
112 	/* PFSYNC_ACT_TDB */		"TDB-replay-counter-update",
113 	/* PFSYNC_ACT_EOF */		"end-of-frame-mark",
114 	/* PFSYNC_ACT_INS_1400 */	"state-insert",
115 	/* PFSYNC_ACT_UPD_1400 */	"state-update",
116 };
117 
118 static void
119 pfsync_acts_stats(const char *list, const char *desc, uint64_t *a)
120 {
121 	int i;
122 
123 	xo_open_list(list);
124 	for (i = 0; i < PFSYNC_ACT_MAX; i++, a++) {
125 		if (*a || sflag <= 1) {
126 			xo_open_instance(list);
127 			xo_emit("\t\t{e:name}{:count/%ju} {N:/%s%s %s}\n",
128 			    pfsyncacts_name[i], (uintmax_t)(*a),
129 			    pfsyncacts[i], plural(*a), desc);
130 			xo_close_instance(list);
131 		}
132 	}
133 	xo_close_list(list);
134 }
135 
136 /*
137  * Dump pfsync statistics structure.
138  */
139 void
140 pfsync_stats(u_long off, const char *name, int af1 __unused, int proto __unused)
141 {
142 	struct pfsyncstats pfsyncstat;
143 
144 	if (fetch_stats("net.pfsync.stats", off, &pfsyncstat,
145 	    sizeof(pfsyncstat), kread) != 0)
146 		return;
147 
148 	xo_emit("{T:/%s}:\n", name);
149 	xo_open_container(name);
150 
151 #define	p(f, m) if (pfsyncstat.f || sflag <= 1) \
152 	xo_emit(m, (uintmax_t)pfsyncstat.f, plural(pfsyncstat.f))
153 
154 	p(pfsyncs_ipackets, "\t{:received-inet-packets/%ju} "
155 	    "{N:/packet%s received (IPv4)}\n");
156 	p(pfsyncs_ipackets6, "\t{:received-inet6-packets/%ju} "
157 	    "{N:/packet%s received (IPv6)}\n");
158 	pfsync_acts_stats("input-histogram", "received",
159 	    &pfsyncstat.pfsyncs_iacts[0]);
160 	p(pfsyncs_badif, "\t\t{:dropped-bad-interface/%ju} "
161 	    "{N:/packet%s discarded for bad interface}\n");
162 	p(pfsyncs_badttl, "\t\t{:dropped-bad-ttl/%ju} "
163 	    "{N:/packet%s discarded for bad ttl}\n");
164 	p(pfsyncs_hdrops, "\t\t{:dropped-short-header/%ju} "
165 	    "{N:/packet%s shorter than header}\n");
166 	p(pfsyncs_badver, "\t\t{:dropped-bad-version/%ju} "
167 	    "{N:/packet%s discarded for bad version}\n");
168 	p(pfsyncs_badauth, "\t\t{:dropped-bad-auth/%ju} "
169 	    "{N:/packet%s discarded for bad HMAC}\n");
170 	p(pfsyncs_badact,"\t\t{:dropped-bad-action/%ju} "
171 	    "{N:/packet%s discarded for bad action}\n");
172 	p(pfsyncs_badlen, "\t\t{:dropped-short/%ju} "
173 	    "{N:/packet%s discarded for short packet}\n");
174 	p(pfsyncs_badval, "\t\t{:dropped-bad-values/%ju} "
175 	    "{N:/state%s discarded for bad values}\n");
176 	p(pfsyncs_stale, "\t\t{:dropped-stale-state/%ju} "
177 	    "{N:/stale state%s}\n");
178 	p(pfsyncs_badstate, "\t\t{:dropped-failed-lookup/%ju} "
179 	    "{N:/failed state lookup\\/insert%s}\n");
180 	p(pfsyncs_opackets, "\t{:sent-inet-packets/%ju} "
181 	    "{N:/packet%s sent (IPv4})\n");
182 	p(pfsyncs_opackets6, "\t{:send-inet6-packets/%ju} "
183 	    "{N:/packet%s sent (IPv6})\n");
184 	pfsync_acts_stats("output-histogram", "sent",
185 	    &pfsyncstat.pfsyncs_oacts[0]);
186 	p(pfsyncs_onomem, "\t\t{:discarded-no-memory/%ju} "
187 	    "{N:/failure%s due to mbuf memory error}\n");
188 	p(pfsyncs_oerrors, "\t\t{:send-errors/%ju} "
189 	    "{N:/send error%s}\n");
190 #undef p
191 	xo_close_container(name);
192 }
193 #endif /* PF */
194 
195 /*
196  * Display a formatted value, or a '-' in the same space.
197  */
198 static void
199 show_stat(const char *fmt, int width, const char *name,
200     u_long value, short showvalue, int div1000)
201 {
202 	const char *lsep, *rsep;
203 	char newfmt[64];
204 
205 	lsep = "";
206 	if (strncmp(fmt, "LS", 2) == 0) {
207 		lsep = " ";
208 		fmt += 2;
209 	}
210 	rsep = " ";
211 	if (strncmp(fmt, "NRS", 3) == 0) {
212 		rsep = "";
213 		fmt += 3;
214 	}
215 	if (showvalue == 0) {
216 		/* Print just dash. */
217 		xo_emit("{P:/%s}{D:/%*s}{P:/%s}", lsep, width, "-", rsep);
218 		return;
219 	}
220 
221 	/*
222 	 * XXX: workaround {P:} modifier can't be empty and doesn't seem to
223 	 * take args... so we need to conditionally include it in the format.
224 	 */
225 #define maybe_pad(pad)	do {						    \
226 	if (strlen(pad)) {						    \
227 		snprintf(newfmt, sizeof(newfmt), "{P:%s}", pad);	    \
228 		xo_emit(newfmt);					    \
229 	}								    \
230 } while (0)
231 
232 	if (hflag) {
233 		char buf[5];
234 
235 		/* Format in human readable form. */
236 		humanize_number(buf, sizeof(buf), (int64_t)value, "",
237 		    HN_AUTOSCALE, HN_NOSPACE | HN_DECIMAL | \
238 		    ((div1000) ? HN_DIVISOR_1000 : 0));
239 		maybe_pad(lsep);
240 		snprintf(newfmt, sizeof(newfmt), "{:%s/%%%ds}", name, width);
241 		xo_emit(newfmt, buf);
242 		maybe_pad(rsep);
243 	} else {
244 		/* Construct the format string. */
245 		maybe_pad(lsep);
246 		snprintf(newfmt, sizeof(newfmt), "{:%s/%%%d%s}",
247 		    name, width, fmt);
248 		xo_emit(newfmt, value);
249 		maybe_pad(rsep);
250 	}
251 }
252 
253 /*
254  * Find next multiaddr for a given interface name.
255  */
256 static struct ifmaddrs *
257 next_ifma(struct ifmaddrs *ifma, const char *name, const sa_family_t family)
258 {
259 
260 	for(; ifma != NULL; ifma = ifma->ifma_next) {
261 		struct sockaddr_dl *sdl;
262 
263 		sdl = (struct sockaddr_dl *)ifma->ifma_name;
264 		if (ifma->ifma_addr->sa_family == family &&
265 		    strcmp(sdl->sdl_data, name) == 0)
266 			break;
267 	}
268 
269 	return (ifma);
270 }
271 
272 /*
273  * Print a description of the network interfaces.
274  */
275 void
276 intpr(void (*pfunc)(char *), int af)
277 {
278 	struct ifaddrs *ifap, *ifa;
279 	struct ifmaddrs *ifmap, *ifma;
280 	u_int ifn_len_max = 5, ifn_len;
281 	u_int has_ipv6 = 0, net_len = 13, addr_len = 17;
282 
283 	if (interval)
284 		return sidewaysintpr();
285 
286 	if (getifaddrs(&ifap) != 0)
287 		err(EX_OSERR, "getifaddrs");
288 	if (aflag && getifmaddrs(&ifmap) != 0)
289 		err(EX_OSERR, "getifmaddrs");
290 
291 	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
292 		if (interface != NULL &&
293 		    strcmp(ifa->ifa_name, interface) != 0)
294 			continue;
295 		if (af != AF_UNSPEC && ifa->ifa_addr->sa_family != af)
296 			continue;
297 		ifn_len = strlen(ifa->ifa_name);
298 		if ((ifa->ifa_flags & IFF_UP) == 0)
299 			++ifn_len;
300 		ifn_len_max = MAX(ifn_len_max, ifn_len);
301 		if (ifa->ifa_addr->sa_family == AF_INET6)
302 			has_ipv6 = 1;
303 	}
304 	if (Wflag) {
305 		if (has_ipv6) {
306 			net_len = 24;
307 			addr_len = 39;
308 		} else
309 			net_len = 18;
310 	}
311 
312 	xo_open_list("interface");
313 	if (!pfunc) {
314 		xo_emit("{T:/%-*.*s}", ifn_len_max, ifn_len_max, "Name");
315 		xo_emit(" {T:/%5.5s} {T:/%-*.*s} {T:/%-*.*s} {T:/%8.8s} "
316 		    "{T:/%5.5s} {T:/%5.5s}",
317 		    "Mtu", net_len, net_len, "Network", addr_len, addr_len,
318 		    "Address", "Ipkts", "Ierrs", "Idrop");
319 		if (bflag)
320 			xo_emit(" {T:/%10.10s}","Ibytes");
321 		xo_emit(" {T:/%8.8s} {T:/%5.5s}", "Opkts", "Oerrs");
322 		if (bflag)
323 			xo_emit(" {T:/%10.10s}","Obytes");
324 		xo_emit(" {T:/%5s}", "Coll");
325 		if (dflag)
326 			xo_emit(" {T:/%5.5s}", "Drop");
327 		xo_emit("\n");
328 	}
329 
330 	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
331 		bool network = false, link = false;
332 		char *name, *xname, buf[IFNAMSIZ+1];
333 		const char *nn, *rn;
334 
335 		if (interface != NULL && strcmp(ifa->ifa_name, interface) != 0)
336 			continue;
337 
338 		name = ifa->ifa_name;
339 
340 		if (pfunc) {
341 
342 			(*pfunc)(name);
343 
344 			/*
345 			 * Skip all ifaddrs belonging to same interface.
346 			 */
347 			while(ifa->ifa_next != NULL &&
348 			    (strcmp(ifa->ifa_next->ifa_name, name) == 0)) {
349 				ifa = ifa->ifa_next;
350 			}
351 			continue;
352 		}
353 
354 		if (af != AF_UNSPEC && ifa->ifa_addr->sa_family != af)
355 			continue;
356 
357 		xo_open_instance("interface");
358 
359 		if ((ifa->ifa_flags & IFF_UP) == 0) {
360 			xname = stpcpy(buf, name);
361 			*xname++ = '*';
362 			*xname = '\0';
363 			xname = buf;
364 		} else
365 			xname = name;
366 
367 		xo_emit("{d:/%-*.*s}{etk:name}{eq:flags/0x%x}",
368 		    ifn_len_max, ifn_len_max, xname, name, ifa->ifa_flags);
369 
370 #define IFA_MTU(ifa)	(((struct if_data *)(ifa)->ifa_data)->ifi_mtu)
371 		show_stat("lu", 6, "mtu", IFA_MTU(ifa), IFA_MTU(ifa), 0);
372 #undef IFA_MTU
373 
374 		switch (ifa->ifa_addr->sa_family) {
375 		case AF_UNSPEC:
376 			xo_emit("{:network/%-*.*s} ", net_len, net_len,
377 			    "none");
378 			xo_emit("{:address/%-*.*s} ", addr_len, addr_len,
379 			    "none");
380 			break;
381 		case AF_INET:
382 #ifdef INET6
383 		case AF_INET6:
384 #endif /* INET6 */
385 			nn = netname(ifa->ifa_addr, ifa->ifa_netmask);
386 			rn = routename(ifa->ifa_addr, numeric_addr);
387 			if (Wflag) {
388 				xo_emit("{t:network/%-*s} ", net_len, nn);
389 				xo_emit("{t:address/%-*s} ", addr_len, rn);
390 			} else {
391 				xo_emit("{d:network/%-*.*s}{et:network} ",
392 				    net_len, net_len, nn, nn);
393 				xo_emit("{d:address/%-*.*s}{et:address} ",
394 				    addr_len, addr_len, rn, rn);
395 			}
396 
397 			network = true;
398 			break;
399 		case AF_LINK:
400 		    {
401 			struct sockaddr_dl *sdl;
402 			char linknum[sizeof("<Link#32767>")];
403 
404 			sdl = (struct sockaddr_dl *)ifa->ifa_addr;
405 			snprintf(linknum, sizeof(linknum), "<Link#%d>", sdl->sdl_index);
406 			xo_emit("{t:network/%-*.*s} ", net_len, net_len,
407 			    linknum);
408 			if (sdl->sdl_nlen == 0 &&
409 			    sdl->sdl_alen == 0 &&
410 			    sdl->sdl_slen == 0)
411 				xo_emit("{P:/%*s} ", addr_len, "");
412 			else
413 				xo_emit("{t:address/%-*.*s} ", addr_len,
414 				    addr_len, routename(ifa->ifa_addr, 1));
415 			link = true;
416 			break;
417 		    }
418 		}
419 
420 #define	IFA_STAT(s)	(((struct if_data *)ifa->ifa_data)->ifi_ ## s)
421 		show_stat("lu", 8, "received-packets", IFA_STAT(ipackets),
422 		    link|network, 1);
423 		show_stat("lu", 5, "received-errors", IFA_STAT(ierrors),
424 		    link, 1);
425 		show_stat("lu", 5, "dropped-packets", IFA_STAT(iqdrops),
426 		    link, 1);
427 		if (bflag)
428 			show_stat("lu", 10, "received-bytes", IFA_STAT(ibytes),
429 			    link|network, 0);
430 		show_stat("lu", 8, "sent-packets", IFA_STAT(opackets),
431 		    link|network, 1);
432 		show_stat("lu", 5, "send-errors", IFA_STAT(oerrors), link, 1);
433 		if (bflag)
434 			show_stat("lu", 10, "sent-bytes", IFA_STAT(obytes),
435 			    link|network, 0);
436 		show_stat("NRSlu", 5, "collisions", IFA_STAT(collisions),
437 		    link, 1);
438 		if (dflag)
439 			show_stat("LSlu", 5, "dropped-packets",
440 			    IFA_STAT(oqdrops), link, 1);
441 		xo_emit("\n");
442 
443 		if (!aflag) {
444 			xo_close_instance("interface");
445 			continue;
446 		}
447 
448 		/*
449 		 * Print family's multicast addresses.
450 		 */
451 		xo_open_list("multicast-address");
452 		for (ifma = next_ifma(ifmap, ifa->ifa_name,
453 		    ifa->ifa_addr->sa_family);
454 		    ifma != NULL;
455 		    ifma = next_ifma(ifma, ifa->ifa_name,
456 		    ifa->ifa_addr->sa_family)) {
457 			const char *fmt = NULL;
458 
459 			xo_open_instance("multicast-address");
460 			switch (ifma->ifma_addr->sa_family) {
461 			case AF_LINK:
462 			    {
463 				struct sockaddr_dl *sdl;
464 
465 				sdl = (struct sockaddr_dl *)ifma->ifma_addr;
466 				if (sdl->sdl_type != IFT_ETHER &&
467 				    sdl->sdl_type != IFT_FDDI)
468 					break;
469 			    }
470 				/* FALLTHROUGH */
471 			case AF_INET:
472 #ifdef INET6
473 			case AF_INET6:
474 #endif /* INET6 */
475 				fmt = routename(ifma->ifma_addr, numeric_addr);
476 				break;
477 			}
478 			if (fmt) {
479 				if (Wflag)
480 					xo_emit("{P:/%27s }"
481 					    "{t:address/%-17s/}", "", fmt);
482 				else
483 					xo_emit("{P:/%25s }"
484 					    "{t:address/%-17.17s/}", "", fmt);
485 				if (ifma->ifma_addr->sa_family == AF_LINK) {
486 					xo_emit(" {:received-packets/%8lu}",
487 					    IFA_STAT(imcasts));
488 					xo_emit("{P:/%*s}", bflag? 17 : 6, "");
489 					xo_emit(" {:sent-packets/%8lu}",
490 					    IFA_STAT(omcasts));
491  				}
492 				xo_emit("\n");
493 			}
494 			xo_close_instance("multicast-address");
495 			ifma = ifma->ifma_next;
496 		}
497 		xo_close_list("multicast-address");
498 		xo_close_instance("interface");
499 	}
500 	xo_close_list("interface");
501 
502 	freeifaddrs(ifap);
503 	if (aflag)
504 		freeifmaddrs(ifmap);
505 }
506 
507 struct iftot {
508 	u_long	ift_ip;			/* input packets */
509 	u_long	ift_ie;			/* input errors */
510 	u_long	ift_id;			/* input drops */
511 	u_long	ift_op;			/* output packets */
512 	u_long	ift_oe;			/* output errors */
513 	u_long	ift_od;			/* output drops */
514 	u_long	ift_co;			/* collisions */
515 	u_long	ift_ib;			/* input bytes */
516 	u_long	ift_ob;			/* output bytes */
517 };
518 
519 /*
520  * Obtain stats for interface(s).
521  */
522 static void
523 fill_iftot(struct iftot *st)
524 {
525 	struct ifaddrs *ifap, *ifa;
526 	bool found = false;
527 
528 	if (getifaddrs(&ifap) != 0)
529 		xo_err(EX_OSERR, "getifaddrs");
530 
531 	bzero(st, sizeof(*st));
532 
533 	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
534 		if (ifa->ifa_addr->sa_family != AF_LINK)
535 			continue;
536 		if (interface) {
537 			if (strcmp(ifa->ifa_name, interface) == 0)
538 				found = true;
539 			else
540 				continue;
541 		}
542 
543 		st->ift_ip += IFA_STAT(ipackets);
544 		st->ift_ie += IFA_STAT(ierrors);
545 		st->ift_id += IFA_STAT(iqdrops);
546 		st->ift_ib += IFA_STAT(ibytes);
547 		st->ift_op += IFA_STAT(opackets);
548 		st->ift_oe += IFA_STAT(oerrors);
549 		st->ift_od += IFA_STAT(oqdrops);
550 		st->ift_ob += IFA_STAT(obytes);
551  		st->ift_co += IFA_STAT(collisions);
552 	}
553 
554 	if (interface && found == false)
555 		xo_err(EX_DATAERR, "interface %s not found", interface);
556 
557 	freeifaddrs(ifap);
558 }
559 
560 /*
561  * Set a flag to indicate that a signal from the periodic itimer has been
562  * caught.
563  */
564 static sig_atomic_t signalled;
565 static void
566 catchalarm(int signo __unused)
567 {
568 	signalled = true;
569 }
570 
571 /*
572  * Print a running summary of interface statistics.
573  * Repeat display every interval seconds, showing statistics
574  * collected over that interval.  Assumes that interval is non-zero.
575  * First line printed at top of screen is always cumulative.
576  */
577 static void
578 sidewaysintpr(void)
579 {
580 	struct iftot ift[2], *new, *old;
581 	struct itimerval interval_it;
582 	int oldmask, line;
583 
584 	new = &ift[0];
585 	old = &ift[1];
586 	fill_iftot(old);
587 
588 	(void)signal(SIGALRM, catchalarm);
589 	signalled = false;
590 	interval_it.it_interval.tv_sec = interval;
591 	interval_it.it_interval.tv_usec = 0;
592 	interval_it.it_value = interval_it.it_interval;
593 	setitimer(ITIMER_REAL, &interval_it, NULL);
594 	xo_open_list("interface-statistics");
595 
596 banner:
597 	xo_emit("{T:/%17s} {T:/%14s} {T:/%16s}\n", "input",
598 	    interface != NULL ? interface : "(Total)", "output");
599 	xo_emit("{T:/%10s} {T:/%5s} {T:/%5s} {T:/%10s} {T:/%10s} {T:/%5s} "
600 	    "{T:/%10s} {T:/%5s}",
601 	    "packets", "errs", "idrops", "bytes", "packets", "errs", "bytes",
602 	    "colls");
603 	if (dflag)
604 		xo_emit(" {T:/%5.5s}", "drops");
605 	xo_emit("\n");
606 	xo_flush();
607 	line = 0;
608 
609 loop:
610 	if ((noutputs != 0) && (--noutputs == 0)) {
611 		xo_close_list("interface-statistics");
612 		return;
613 	}
614 	oldmask = sigblock(sigmask(SIGALRM));
615 	while (!signalled)
616 		sigpause(0);
617 	signalled = false;
618 	sigsetmask(oldmask);
619 	line++;
620 
621 	fill_iftot(new);
622 
623 	xo_open_instance("stats");
624 	show_stat("lu", 10, "received-packets",
625 	    new->ift_ip - old->ift_ip, 1, 1);
626 	show_stat("lu", 5, "received-errors",
627 	    new->ift_ie - old->ift_ie, 1, 1);
628 	show_stat("lu", 5, "dropped-packets",
629 	    new->ift_id - old->ift_id, 1, 1);
630 	show_stat("lu", 10, "received-bytes",
631 	    new->ift_ib - old->ift_ib, 1, 0);
632 	show_stat("lu", 10, "sent-packets",
633 	    new->ift_op - old->ift_op, 1, 1);
634 	show_stat("lu", 5, "send-errors",
635 	    new->ift_oe - old->ift_oe, 1, 1);
636 	show_stat("lu", 10, "sent-bytes",
637 	    new->ift_ob - old->ift_ob, 1, 0);
638 	show_stat("NRSlu", 5, "collisions",
639 	    new->ift_co - old->ift_co, 1, 1);
640 	if (dflag)
641 		show_stat("LSlu", 5, "dropped-packets",
642 		    new->ift_od - old->ift_od, 1, 1);
643 	xo_close_instance("stats");
644 	xo_emit("\n");
645 	xo_flush();
646 
647 	if (new == &ift[0]) {
648 		new = &ift[1];
649 		old = &ift[0];
650 	} else {
651 		new = &ift[0];
652 		old = &ift[1];
653 	}
654 
655 	if (line == 21)
656 		goto banner;
657 	else
658 		goto loop;
659 
660 	/* NOTREACHED */
661 }
662